Analogic AAT3687IWP-4.2-2-T1 Lithium-ion/polymer battery charger Datasheet

AAT3687
Lithium-Ion/Polymer Battery Charger
General Description
Features
The AAT3687 BatteryManager is a member of
AnalogicTech's Total Power Management IC™
(TPMIC™) product family. This device is a highly
integrated single-cell lithium-ion/polymer battery
charger IC designed to operate with AC adapter
inputs. It requires a minimum number of external
components. The AAT3687 precisely regulates
battery charge voltage and current for 4.2V lithiumion/polymer battery cells. Adapter charge current
rates can be programmed up to 1.5A. An active
thermal management system regulates the fast
charge constant current for all ambient temperature and input vs. output voltage conditions.
•
•
•
•
•
•
•
•
•
•
•
•
•
Battery temperature and charge state are fully
monitored for fault conditions. In the event of an
over-voltage or over-temperature failure, the
device will automatically shut down, thus protecting
the charging device, control system, and the battery under charge. Status monitor output pins are
provided to indicate the battery charge status by
directly driving two external LEDs. A serial interface
output is available to report 12 various charging
status states to a microcontroller.
BatteryManager™
Input Voltage Range: 4.0V to 5.5V
Up to 1.5A Charging Current
Adapter Present Indicator (ADPP#)
High Level of Integration with Internal:
— Charging Device
— Reverse Blocking Diode
— Current Sensing
Active Thermal Loop Charge Reduction
Automatic Recharge Sequencing
Battery Temperature Monitoring
Full Battery Charge Auto Turn-Off / Sleep Mode
Over-Voltage, Over-Temperature, and
Emergency Thermal Protection
Power On Reset and Soft Start
Serial Interface Status Report
12-Pin 3x3mm TDFN Package
-40°C to +85°C Temperature Range
Applications
•
•
•
•
•
•
The AAT3687 is available in a Pb-free, thermallyenhanced, space-saving 12-pin TDFN 3x3mm
package and is rated over the -40°C to +85°C temperature range.
Cellular Telephones
Digital Still Cameras
Hand Held PCs
MP3 Players
Personal Data Assistants (PDAs)
Other Lithium-Ion/Polymer Battery-Powered
Devices
Typical Application
BATT+
Adapter
Present
ADPP#
Enable
BAT
EN
COUT
10μF
DATA
Serial Interface
TS
+
BATT-
AAT3687
CT
Adapter
ADP
ADPSET
CIN
10μF
STAT1
GND
CT
0.1μF
TEMP
STAT2
RSET
RB1
RB2
Battery
Pack
LED1
LED2
3687.2006.06.1.5
1
AAT3687
Lithium-Ion/Polymer Battery Charger
Pin Descriptions
Pin #
Name
Type
Function
1
BAT
Out
2
ADP
In
3
GND
Ground
4
EN
In
AAT3687: Enable pin. Logic high enables the IC.
AAT3687-2: Enable pin. Logic high enables the IC. EN tied to internal
4MΩ pull-up resistor to ADP.
5
ADPP#
Out
Adapter present indicator. This pin is open drain until ADP pin reaches
threshold.
6
TS
In/Out
7
DATA
Out
Status report to microcontroller via serial interface: open drain.
8
STAT2
Out
Battery charge status indicator pin to drive an LED: active low, open drain.
9
STAT1
Out
Battery charge status indicator pin to drive an LED: active low, open drain.
10
CT
In/Out
11
N/C
12
ADPSET
Battery charging and sensing.
Adapter input.
Ground connection.
Connect to 10kΩ NTC thermistor.
Timing capacitor to adjust internal watchdog timer. Set maximum charge
time for adapter powered trickle, CC, and CV charge modes. If timing
function is not needed, terminate this pin to ground.
No connection.
In/Out
EP
Use resistor at this pin to set adapter charging current.
Exposed paddle (bottom); connect to GND directly beneath package.
Pin Configuration
TDFN33-12
(Top View)
BAT
ADP
GND
EN
ADPP#
TS
2
1
12
2
11
3
10
4
9
5
8
6
7
ADPSET
N/C
CT
STAT1
STAT2
DATA
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
AAT3687 Feature Options
Product
Trickle Charge
Internal Pull-Up
Resistor on EN Pin
Can Leave
TS Pin Open
AAT3687
AAT3687-2
Yes
No
No
Yes
No
Yes
Absolute Maximum Ratings1
Symbol
VP
VP
VN
TJ
TLEAD
Description
ADP Input Voltage, <30ms, Duty Cycle <10%
ADP Input Voltage, Continuous
BAT, TS, ADPSET, ADPP#, DATA, CT, EN, STAT1, STAT2
Operating Junction Temperature Range
Maximum Soldering Temperature (at leads)
Value
Units
-0.3 to 7.0
-0.3 to 6.0
-0.3 to VP + 0.3
-40 to 150
300
V
V
V
°C
°C
Value
Units
50
2.0
°C/W
W
Thermal Information
Symbol
θJA
PD
Description
Maximum Thermal Resistance
Maximum Power Dissipation
2
1. Stresses above those listed in Absolute Maximum Ratings may cause permanent damage to the device. Functional operation at conditions other than the operating conditions specified is not implied. Only one Absolute Maximum Rating should be applied at any one time.
2. Mounted on an FR4 board.
3687.2006.06.1.5
3
AAT3687
Lithium-Ion/Polymer Battery Charger
Electrical Characteristics1
VADP = 5V, TA = -25°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol
Operation
ADP
VADPP
VUVLO
IOP
ISLEEP
Description
Adapter Voltage Range
Adapter Present Indicator Threshold
Voltage
Under-Voltage Lockout (UVLO)
UVLO Hysteresis
Operating Current
Sleep Mode Current
Reverse Leakage Current from
BAT Pin
Voltage Regulation
VBAT_EOC1 End of Charge Voltage Accuracy
ΔVCH/VCH Output Charge Voltage Tolerance
VMIN
Preconditioning Voltage Threshold
VRCH
Battery Recharge Voltage Threshold
Current Regulation
ICH
Charge Current
ΔICH/ICH
Charge Current Regulation Tolerance
VADPSET
ADPSET Pin Voltage
KIA
Current Set Factor: ICH/IADPSET
Charging Devices
Adapter Charging Transistor
RDS(ON)
On Resistance
ILeakage
Conditions
Min
Typ
4.0
4.25
Rising Edge
4.5
Charge Current = 100mA
AAT3687: VBAT = 4.25V
AAT3687-2: VBAT = 4.25V
3.0
150
0.75
0.3
1
VBAT = 4V, ADP Pin Open
1.0
4.158
AAT3687 Only
2.8
4.20
0.5
3.0
Max Units
5.5
V
4.7
V
1.5
1.0
3
4.242
3.15
VIN = 5.5V
0.2
0.25
V
%
V
V
1500
mA
%
V
0.35
Ω
10
2.0
4000
CC Mode
μA
μA
VBAT_EOC - 0.1
100
V
mV
mA
1. The AAT3687 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -25°C to +85°C
temperature range is guaranteed by design.
4
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
Electrical Characteristics1
VADP = 5V, TA = -25°C to +85°C, unless otherwise noted. Typical values are at TA = 25°C.
Symbol
Description
Logic Control / Protection
VEN(H)
Input High Threshold
VEN(L)
Input Low Threshold
IEN(H)
EN Input Current
VADPP#
Output Low Voltage
Preconditioning and Constant
TC
Current Mode Time Out
TP
TV
VSTAT
ISTAT
VOVP
ITK/ICHG
ITS
TS1
TS2
IDATA
IADPP#
VDATA(H)
VDATA(L)
SQPULSE
tPERIOD
fDATA
TREG
TLOOP_IN
TLOOP_OUT
TOVSD
Preconditioning Time Out
Conditions
Min
Typ
Max
Units
0.4
10
0.4
V
V
μA
V
1.6
AAT3687-2 Only; VEN = 5V
ADPP# Pin Sinks 500μA
CCT = 100nF, VADP = 5.5V
AAT3687 Only; CCT = 100nF,
VADP = 5.5V
CCT = 100nF, VADP = 5.5V
STAT Pin Sinks 4mA
Constant Voltage Mode Time Out
Output Low Voltage
STAT Pin Current Sink Capability
Over-Voltage Protection Threshold
Pre-Charge Current
AAT3687 Only
Charge Termination Threshold
Current ITERM/ICHG
Current Source from TS Pin
Threshold
TS Hot Temperature Fault
Hysteresis
Threshold
TS Cold Temperature Fault
Hysteresis
DATA Pin Sink Current
DATA Pin is Active Low State
ADPP# Current Sink
ADPP# Pin is Active Low State
Input High Threshold
Input Low Threshold
Status Request Pulse Width
Status Request
System Clock Period
Data Output Frequency
Thermal Loop Regulation
Thermal Loop Entering Threshold
Thermal Loop Exiting Threshold
Over-Temperature Shutdown
Threshold
3.0
Hours
25
Minutes
3.0
8.0
4.4
10
Hours
V
mA
V
%
7.5
%
0.4
70
310
2.2
80
330
15
2.3
10
90
350
2.4
μA
mV
50
20
90
110
85
V
mV
mA
mA
V
V
ns
μs
kHz
°C
°C
°C
145
°C
3
8
1.6
0.4
200
1. The AAT3687 output charge voltage is specified over the 0° to 70°C ambient temperature range; operation over the -25°C to +85°C
temperature range is guaranteed by design.
3687.2006.06.1.5
5
AAT3687
Lithium-Ion/Polymer Battery Charger
Typical Characteristics
IFASTCHARGE vs. RSET
Battery Voltage vs. Supply Voltage
4.242
4.221
1000
VBAT (V)
IFASTCHARGE (mA)
10000
4.200
100
4.179
4.158
10
1
10
4.5
100
4.75
RSET (kΩ
Ω)
5.0
5.25
5.5
Supply Voltage (V)
End of Charge Voltage Regulation
vs. Temperature
Preconditioning Threshold
Voltage vs. Temperature
4.242
3.05
3.04
3.03
3.02
VMIN (V)
VBAT (V)
4.221
4.200
3.01
3.00
2.99
2.98
4.179
2.97
2.96
4.158
-50
2.95
-25
0
25
50
75
-50
100
-25
Temperature (°°C)
0
25
50
75
100
Temperature (°°C)
Preconditioning ICH vs. Temperature
Fast Charge Current vs. Temperature
(ADPSET = 8.06kΩ
Ω)
(ADPSET = 8.06kΩ
Ω)
1100
120
1060
110
ICH ADP (mA)
ICH ADP (mA)
1080
100
90
1040
1020
1000
980
960
940
920
80
-50
900
-25
0
25
50
Temperature (°C)
6
75
100
-50
-25
0
25
50
75
100
Temperature (°C)
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
Typical Characteristics
Charging Current vs. Battery Voltage
Fast Charge Current vs. Supply Voltage
(ADPSET = 8.06kΩ
Ω; VIN = 5.0V)
(ADPSET = 8.06kΩ
Ω)
1.2
1200
1.0
1000
0.8
800
ICH (mA)
ICH (A)
VBAT = 3.3V
0.6
0.4
0.2
600
VBAT = 3.9V
VBAT = 3.5V
400
200
0.0
2.5
2.9
3.3
3.7
4.1
0
4.0
4.5
4.5
Battery Voltage (V)
6.0
VIL vs. Supply Voltage
EN Pin (Falling)
1.4
1.4
1.3
1.3
1.2
1.2
1.1
1.1
-40°C
1.0
+25°C
VIH (V)
VIH (V)
5.5
Supply Voltage (V)
VIH vs. Supply Voltage
EN Pin (Rising)
0.9
0.8
0.7
-40°C
1.0
+25°C
0.9
0.8
0.7
+85°C
0.6
0.6
+85°C
0.5
0.5
0.4
0.4
4.2
4.4
4.6
4.8
5.0
5.2
5.4
5.6
5.8
6.0
4.2
4.4
4.6
Supply Voltage (V)
5.2
5.4
5.6
5.8
6.0
(CT = 0.1μ
μF)
8
Counter Timeout (%)
10
0.70
0.60
Constant Current
0.40
0.30
0.20
5.0
Counter Timeout vs. Temperature
0.80
0.50
4.8
Supply Voltage (V)
Adapter Mode Supply Current
vs. ADPSET Resistor
IQ (mA)
5.0
Pre-Conditioning
0.10
6
4
2
0
-2
-4
-6
-8
0.00
1
10
100
ADPSET Resistor (kΩ
Ω)
3687.2006.06.1.5
1000
-10
-50
-25
0
25
50
75
100
Temperature (°C)
7
AAT3687
Lithium-Ion/Polymer Battery Charger
Typical Characteristics
CT Pin Capacitance vs. Counter Timeout
Temperature Sense Output Current
vs. Temperature
2.0
88
TS Pin Current (μA)
Capacitance (μ
μF)
1.8
1.6
1.4
Precondition Timeout
1.2
1.0
0.8
Precondition + Constant Current Timeout
or Constant Voltage Timeout
0.6
0.4
0.2
84
82
80
78
76
74
72
0.0
0
2
4
6
Time (hours)
8
86
8
10
-50
-25
0
25
50
75
100
Temperature (°°C)
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
Functional Block Diagram
CV/
Precharge1
Constant
Current
Charge
Control
4.2V
BAT
OverTemperature
Protection
Current
Compare
ADPSET
UVLO
ADP
ADPP#
Voltage
Sense
Reverse Blocking
80μA
STAT1
STAT2
DATA
TS
Charge
Status
Serial
Data
Window
Comparator
IC enable
Watchdog
Timer
CT
EN
GND
Functional Description
The AAT3687 is a highly integrated single-cell lithiumion/polymer battery charger IC designed to operate
with standard AC adapter input sources, while requiring a minimum number of external components. The
AAT3687 precisely regulates battery charge voltage
and current for 4.2V lithium-ion/polymer battery cells.
The adapter charge input constant current level can
be programmed up to 1.5A for rapid charging applications. The AAT3687 is rated for operation from 40°C to +85°C. In the event of operating ambient
temperatures exceeding the power dissipation abilities of the device package for a given constant current
charge level, the charge control will enter into thermal
regulation. When the system thermal regulation
becomes active, the programmed constant current
charge amplitude will be automatically reduced to a
safe level for the current operating condition. Should
the ambient operating temperature drop below the
thermal loop threshold, the system will automatically
resume charging at the full programmed constant cur-
rent level. This intelligent thermal management system permits the AAT3687 to operate and safely
charge a battery cell over a wide range of ambient
conditions while maximizing the greatest possible
charge current for the given set of conditions.
Status monitor output pins are provided to indicate
the battery charge state by directly driving two external LEDs. A serial interface output is also available to
report any one of 12 distinct charge states to the system microcontroller.
Battery temperature and charge state are fully monitored for fault conditions. In the event of an over-voltage or over-temperature failure, the device will automatically shut down, thus protecting the charging
device, control system, and the battery under charge.
In addition to internal charge controller thermal protection, the AAT3687 also provides a temperature
sense feedback function (TS pin) from the battery to
shut down the device in the event the battery
exceeds its own thermal limit during charging. All
fault events are reported to the user either by the
simple status LEDs or via the DATA pin function.
1. Precharge applies to AAT3687 only.
3687.2006.06.1.5
9
AAT3687
Lithium-Ion/Polymer Battery Charger
Charge Complete Voltage
Preconditioning
Trickle Charge
Phase
Constant Current
Charge Phase
Constant Voltage
Charge Phase
I = Max CC
Regulated Current
Constant Current Mode
Voltage Threshold
Trickle Charge and
Termination Threshold
I = CC / 10
Figure 1: Current vs. Voltage Profile During Charging Phases.
Charging Operation
The AAT3687 has four basic modes for the battery
charge cycle: pre-conditioning / trickle charge; constant current / fast charge; constant voltage; and
end of charge (see Figure 1.) (AAT3687-2 does not
have trickle charge.)
Battery Preconditioning
Before the start of charging, the AAT3687 checks
several conditions in order to assure a safe charging
environment. The input supply must be above the
minimum operating voltage, or under-voltage lockout
threshold (VUVLO), for the charging sequence to
begin. Also, the cell temperature, as reported by a
thermistor connected to the TS pin from the battery,
must be within the proper window for safe charging.
When these conditions have been met and a battery
is connected to the BAT pin, the AAT3687 checks the
state of the battery. If the cell voltage is below the
preconditioning voltage threshold (VMIN), the charge
control begins preconditioning the cell.
The battery preconditioning trickle charge current is
equal to the fast charge constant current divided by
10. For example, if the programmed fast charge
current is 1.5A, then the preconditioning mode
(trickle charge) current will be 150mA. Cell preconditioning is a safety precaution for deeply discharged battery cells and also aids in limiting power
dissipation in the pass transistor when the voltage
across the device is at the greatest potential.
Fast Charge / Constant Current Charging
Battery cell preconditioning continues until the voltage on the BAT pin exceeds the preconditioning
voltage threshold (VMIN). At this point, the AAT3687
begins the constant current fast charging phase.
10
The fast charge constant current (ICC) amplitude is
programmed by the user via the RSET, resistor. The
AAT3687 remains in the constant current charge
mode until the battery reaches the voltage regulation point, VBAT.
Constant Voltage Charging
The system transitions to a constant voltage charging mode when the battery voltage reaches the
output charge regulation threshold (VBAT) during
the constant current fast charge phase. The regulation voltage level is factory programmed to 4.2V
(±1%). Charge current in the constant voltage
mode drops as the battery cell under charge reaches its maximum capacity.
End of Charge Cycle Termination and Recharge
Sequence
When the charge current drops to 7.5% of the programmed fast charge current level in the constant
voltage mode, the device terminates charging and
goes into a sleep state. The charger will remain in
a sleep state until the battery voltage decreases to
a level below the battery recharge voltage threshold (VRCH).
When the input supply is disconnected, the charger will automatically transition into a power-saving
sleep mode. Only consuming an ultra-low 0.3μA in
sleep mode (1μA for AAT3687-2), the AAT3687
minimizes battery drain when it is not charging.
This feature is particularly useful in applications
where the input supply level may fall below the battery charge or under-voltage lockout level. In such
cases where the AAT3687 input voltage drops, the
device will enter sleep mode and automatically
resume charging once the input supply has recovered from the fault condition.
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
System Operation Flow Chart
Yes
Output
ADPP
ADP
Voltage
ADP > VADPP
Yes
Yes
UVLO
VP > VUVLO
Switch
No
No
Power On
Reset
No
Sleep
Mode
Enable
ADP
Loop
Thermal
Loop
No
Device
Temperature
Monitor
TJ > 110°C
Timing
Fault
Conditions Monitor
OV, OT
Yes
No
Shut Down
Yes
Recharge Test
VRCH > VBAT
Yes (AAT3687-2)
No
Battery
Temperature Monitor
VTS1 < TS < VTS2
No
Yes
Thermal Loop
Current
Reduction
Battery
Temperature
Charge
Safety Timer
Yes (AAT3687)
Preconditioning Test
VMIN > VBAT
Yes
Expire
Low Current
Conditioning
Set
No
Current Phase Test
VCH > VBAT
Yes
Current
Charging
Mode
Yes
Voltage
Charging
Mode
No
Voltage Phase Test
IBAT > IMIN
No
Charge
Completed
Application Information
Adapter Power Input
Constant current charge levels up to 1.5A may be
programmed by the user when powered from a sufficient input power source. The AAT3687 will operate from the adapter input over a 4.0V to 5.5V
range.
3687.2006.06.1.5
The constant current fast charge current for the
adapter input is set by the RSET resistor connected
between the ADPSET and ground. Refer to Table 1
for recommended RSET values for a desired constant current charge level. The presence of voltage
on the adapter input is indicated by the ADPP# pin
function. This indicator pin uses an internal open
drain device that will pull the ADPP# pin low when
11
AAT3687
Lithium-Ion/Polymer Battery Charger
voltage is detected on the ADP pin. The precise
charging function of the AAT3687 may be read from
the DATA pin and/or status LEDs. Please refer to
the Battery Charge Status Indication discussion for
further details on data reporting.
Thermal Loop Control
Due to the integrated nature of the linear charging
control pass device for the adapter input, a special
thermal loop control system has been employed to
maximize charging current under all operating conditions. The thermal management system measures the internal circuit die temperature and reduces
the fast charge current when the device exceeds a
preset internal temperature control threshold. Once
the thermal loop control becomes active, the fast
charge current is initially reduced by a factor of 0.44.
The initial thermal loop current can be estimated by
the following equation:
Eq. 1:
ITLOOP = ICC · 0.44
The thermal loop control re-evaluates the circuit die
temperature in 330ms intervals and adjusts the fast
charge current back up in small steps to the full fast
charge current level or until an equilibrium current
is discovered and maximized for the given ambient
temperature condition. The thermal loop controls
the system charge level; therefore, the AAT3687
will always provide the highest level of constant
current in the fast charge mode possible for any
given ambient temperature condition.
Adapter Input Charge Inhibit and Resume
The AAT3687 has a UVLO and power on reset feature so that the charger will suspend charging and
shut down if the input supply to the adapter pin
drops below the UVLO threshold. When power is
re-applied to the adapter pin or the UVLO conditions recovers, the system charge control will
assess the state of charge on the battery cell and
will automatically resume charging in the appropriate mode for the condition of the battery.
12
Enable / Disable
The AAT3687 provides an enable function to control
the charger IC on and off. The enable (EN) pin is
active high. When pulled to a logic low level, the
AAT3687 will be shut down and forced into the sleep
state. Charging will be halted regardless of the battery voltage or charging state. When the device is reenabled, the charge control circuit will automatically
reset and resume charging functions with the appropriate charging mode based on the battery charge
state and measured cell voltage on the BAT pin.
Programming Charge Current
The fast charge constant current charge level is
user programmed with a set resistor placed
between the ADPSET pin and ground. The accuracy of the fast charge, as well as the preconditioning trickle charge current, is dominated by the
tolerance of the set resistor used. For this reason,
a 1% tolerance metal film resistor is recommended
for the set resistor function.
Fast charge constant current levels from 50mA to
1.5A can be set by selecting the appropriate resistor value from Table 1.
ICC
ADP
Ω)
RSET (kΩ
50
75
100
200
300
400
500
600
700
N/A
N/A
84.5
43.2
28.0
21.0
16.9
13.3
11.5
ICC
ADP
Ω)
RSET (kΩ
800
900
1000
1100
1200
1300
1400
1500
10.2
9.09
8.06
7.32
6.65
6.04
5.62
5.36
Table 1: Recommended RSET Values.
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
pin to ground. The CT pin should not be left floating or un-terminated, as this will cause errors in the
internal timing control circuit.
IFASTCHARGE (mA)
10000
1000
100
10
1
10
100
RSET (kΩ
Ω)
Figure 2: IFASTCHARGE vs. RSET.
Protection Circuitry
Programmable Watchdog Timer
The AAT3687 contains a watchdog timing circuit to
shut down charging functions in the event of a defective battery cell not accepting a charge over a preset
period of time. Typically, a 0.1μF ceramic capacitor
is connected between the CT pin and ground. When
a 0.1μF ceramic capacitor is used, the device will
time out a shutdown condition if the trickle charge
mode exceeds 25 minutes (AAT3687 only) and a
combined trickle charge plus fast charge mode of 3
hours. When the device transitions to the constant
voltage mode, the timing counter is reset and will
time out after an additional 3 hours if the charge current does not drop to the charge termination level.
Mode
Trickle Charge (TC) Time Out
Trickle Charge (TC) +
Fast Charge (CC) Time Out
Constant Voltage (VC) Mode
Time Out
Time
25 minutes
(AAT3687 only)
3 hours
3 hours
Table 2: Summary for a 0.1μF Ceramic
Capacitor Used for the Timing Capacitor.
The CT pin is driven by a constant current source
and will provide a linear response to increases in the
timing capacitor value. Thus, if the timing capacitor
were to be doubled from the nominal 0.1μF value,
the time-out periods would be doubled.
If the programmable watchdog timer function is not
needed, it can be disabled by terminating the CT
3687.2006.06.1.5
The constant current provided to charge the timing
capacitor is very small, and this pin is susceptible
to noise and changes in capacitance value.
Therefore, the timing capacitor should be physically located on the printed circuit board layout as
close as possible to the CT pin. Since the accuracy of the internal timer is dominated by the capacitance value, a 10% tolerance or better ceramic
capacitor is recommended. Ceramic capacitor
materials, such as X7R and X5R types, are a good
choice for this application.
Over-Voltage Protection
An over-voltage event is defined as a condition
where the voltage on the BAT pin exceeds the
maximum battery charge voltage and is set by the
over-voltage protection threshold (VOVP). If an
over-voltage condition occurs, the AAT3687 charge
control will shut down the device until the voltage
on the BAT pin drops below VOVP. The AAT3687
will resume normal charging operation after the
over-voltage condition is removed. During an overvoltage event, the STAT LEDs will report a system
fault, and the actual fault condition can be read via
the DATA pin signal.
Over-Temperature Shutdown
The AAT3687 has a thermal protection control circuit which will shut down charging functions should
the internal die temperature exceed the preset
thermal limit threshold.
Battery Temperature Fault Monitoring
In the event of a battery over-temperature condition, the charge control will turn off the internal pass
device and report a battery temperature fault on the
DATA pin function. The STAT LEDs will also display a system fault. After the system recovers from
a temperature fault, the device will resume charging operation.
The AAT3687 checks battery temperature before
starting the charge cycle, as well as during all
stages of charging. This is accomplished by monitoring the voltage at the TS pin. This system is
intended for use with negative temperature coefficient thermistors (NTC) which are typically integrated into the battery package. Most of the commonly used NTC thermistors in battery packs are
13
AAT3687
Lithium-Ion/Polymer Battery Charger
approximately 10kΩ at room temperature (25°C).
The TS pin has been specifically designed to
source 80μA of current to the thermistor. The voltage on the TS pin resulting from the resistive load
should stay within a window of 335mV to 2.32V. If
the battery becomes too hot during charging due to
an internal fault or excessive fast charge current,
the thermistor will heat up and reduce in value,
pulling the TS pin voltage lower than the TS1
threshold, and the AAT3687 will signal the fault
condition.
If the use of the TS pin function is not required by
the system, it should be terminated to ground using
a 10kΩ resistor. Alternatively, on the AAT3687-2,
the TS pin may be left open.
Battery Charge Status Indication
The AAT3687 indicates the status of the battery
under charge with two different systems. First, the
device has two status LED driver outputs. These
two LEDs can indicate simple functions such as no
battery charge activity, battery charging, charge
complete, and charge fault. The AAT3687 also
provides a bi-directional data reporting function so
that a system microcontroller can interrogate the
DATA pin and read any one of 12 system states.
Status Indicator Display
Simple system charging status states can be displayed using one or two LEDs in conjunction with
the STAT1 and STAT2 pins on the AAT3687.
These two pins are simple open drain switches
used to connect the LED cathodes to ground. It is
not necessary to use both display LEDs if a user
simply wants to have a single lamp to show "charging" or "not charging."
This can be accomplished by using the STAT1 pin
and a single LED. Using two LEDs and both STAT
pins simply gives the user more information to the
charging states. Refer to Table 3 for LED display
definitions. The LED anodes should be connected
to VADP.
The LEDs should be biased with as little current as
necessary to create reasonable illumination; therefore, a ballast resistor should be placed between
the LED cathodes and the STAT1/2 pins. LED current consumption will add to the overall thermal
power budget for the device package, hence it is
good to keep the LED drive current to a minimum.
2mA should be sufficient to drive most low-cost
green or red LEDs. It is not recommended to
exceed 8mA for driving an individual status LED.
The required ballast resistor values can be estimated using the following formulas:
Eq. 2: RB(STAT1/2) =
(VADP - VF(LED))
ILED(STAT1/2)
Example:
Eq. 3: RB(STAT1) =
(5.5V - 2.0V)
= 1.75kΩ
2mA
Note: Red LED forward voltage (VF) is typically
2.0V @ 2mA
Event Description
Charge Disabled or Low Supply
Charge Enabled Without Battery
Battery Charging
Charge Completed
Fault
STAT1
STAT2
Off
Flash1
On
Off
On
Off
Flash1
Off
On
On
Table 3: LED Status Indicator.
1. Flashing rate depends on output capacitance.
14
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
Digital Charge Status Reporting
output, and to maintain the integrity of the data timing for the system, the pull-up resistor on the data
line should be low enough in value so that the
DATA signal returns to the high state without delay.
If the pull-up resistor is too high, the strobe pulse
from the system microcontroller could exceed the
maximum pulse time and the DATA output control
could issue false status reports. A 1.5kΩ resistor is
recommended when pulling the DATA pin high to
5.0V on the VADP input. If the data line is pulled
high to a voltage level less than 5.0V, the pull-up
resistor can be calculated based on a recommended minimum pull-up current of 3mA. Use the following formula:
The AAT3687 has a comprehensive digital data
reporting system by use of the DATA pin feature.
This function can provide detailed information
regarding the status of the charging system. The
DATA pin is a bi-directional port which will read
back a series of data pulses when the system
microcontroller asserts a request pulse. This single strobe request protocol will invoke one of 12
possible return pulse counts that the system microcontroller can look up based on the serial report
data listed in Table 4.
The DATA pin function logic is active low and
should normally be pulled high to VADP. This data
line can also be pulled high to the same level as the
high state for the logic I/O port on the system
microcontroller. In order for the DATA pin control
circuit to generate clean, sharp edges for the data
Eq. 4: RPULL-UP ≤
VPULL-UP
3mA
1.8V to 5.0V
IN
AAT3687
Status
Control
RPULL_UP
IN
DATA Pin
GPIO
OUT
OUT
μP GPIO
Port
Figure 3: Data Pin Application Circuit.
Data Timing
The system microcontroller should assert an active
low data request pulse for minimum duration of
200ns; this is specified by TLO(DATA). Upon sensing
the rising edge of the end of the data request pulse,
3687.2006.06.1.5
the AAT3687 status data control will reply the data
word back to the system microcontroller after a
delay specified by the data report time specification
TDATA(RPT). The period of the following group of
data pulses will be specified by TDATA.
15
AAT3687
Lithium-Ion/Polymer Battery Charger
Timing Diagram
SQ
SQPULSE
PDATA
System Reset
System Start
CK
TSYNC
Data
TLAT
TDATA(RPT) = TSYNC + TLAT < 2.5 PDATA
TOFF > 2 PDATA
TOFF
N=1
N=2
N=3
N
DATA Report Status
1
Chip Over-Temperature Shutdown.
2
Battery Temperature Fault.
3
Over-Voltage Turn Off.
4
Not Used.
5
ADP Watchdog Time-Out in Battery Condition Mode.
6
ADP Battery Condition Mode.
7
ADP Watchdog Time-Out in Constant Current Mode.
8
ADP Thermal Loop Regulation in Constant Current Mode.
9
ADP Constant Current Mode.
10
ADP Watchdog Time-Out in Constant Voltage Mode.
11
ADP Constant Voltage Mode.
12
ADP End of Charging.
23
Data Report Error.
Table 4: Serial Data Report Table.
16
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
Thermal Considerations
Where:
The AAT3687 is offered in a 3x3mm TDFN package which can provide up to 2.0W of power dissipation when it is properly bonded to a printed circuit board and has a maximum thermal resistance
of 50°C/W. Many considerations should be taken
into account when designing the printed circuit
board layout, as well as the placement of the
charger IC package in proximity to other heat generating devices in a given application design. The
ambient temperature around the charger IC will
also have an effect on the thermal limits of a battery charging application. The maximum limits that
can be expected for a given ambient condition can
be estimated by the following discussion.
TA = Ambient Temperature in °C
First, the maximum power dissipation for a given
situation should be calculated:
TJ = Maximum Device Junction Temperature
Below the Thermal Loop Threshold
PD = Total Power Dissipation by the Device
θJA = Package Thermal Resistance in °C/W
Example:
For an application where the fast charge current for
the adapter mode is set to 1A, VADP = 5.0V and the
battery voltage at 3.6V, what is the maximum ambient temperature at which the thermal loop will
become active?
Given:
VADP = 5.0V
VBAT = 3.6V
Eq. 5: PD = [(VIN - VBAT) · ICC + (VIN · IOP)]
Where:
PD
= Total Power Dissipation by the Device
VIN = Input Voltage Amplitude, VADP
VBAT = Battery Voltage as Seen at the BAT Pin
ICC
= Maximum Constant Fast Charge Current
Programmed for the Application
IOP
= Quiescent Current Consumed by the
Charger IC for Normal Operation
Next, the maximum operating ambient temperature
for a given application can be estimated based on
the thermal resistance of the 3x3mm TDFN package when sufficiently mounted to a PCB layout and
the internal thermal loop temperature threshold.
ICC
= 1A
IOP
= 0.75mA
TJ
= 110°C
θJA = 50°C/W
Using Equation 5, calculate the device power dissipation for the stated condition:
Eq. 7: PD = (5.0V - 3.6V)(1A) + (5.0V · 0.75mA)
= 1.40375W
The maximum ambient temperature before the
AAT3687 thermal loop becomes active can now be
calculated using Equation 6:
Eq. 8: TA = 110°C - (50°C/W · 1.40375W)
Eq. 6: TA = TJ - (θJA · PD)
= 39.8125°C
Therefore, under the stated conditions for this
worst case power dissipation example, the
AAT3687 will enter the thermal loop and lower the
fast charge constant current when the ambient
operating temperature rises above 39.8°C.
3687.2006.06.1.5
17
AAT3687
Lithium-Ion/Polymer Battery Charger
Capacitor Selection
Input Capacitor
In general, it is good design practice to place a
decoupling capacitor between the ADP pin and
ground. An input capacitor in the range of 1μF to
22μF is recommended. If the source supply is
unregulated, it may be necessary to increase the
capacitance to keep the input voltage above the
under-voltage lockout threshold during device
enable and when battery charging is initiated.
If the AAT3687 adapter input is to be used in a system with an external power supply source, such as
a typical AC-to-DC wall adapter, then a CIN capacitor in the range of 10μF should be used. A larger
input capacitor in this application will minimize
switching or power transient effects when the
power supply is "hot plugged" in.
Output Capacitor
The AAT3687 only requires a 1μF ceramic capacitor on the BAT pin to maintain circuit stability. This
value should be increased to 10μF or more if the
battery connection is made any distance from the
charger output. If the AAT3687 is to be used in
applications where the battery can be removed
from the charger, such as with desktop charging
cradles, an output capacitor greater than 10μF may
be required to prevent the device from cycling on
and off when no battery is present.
Printed Circuit Board Layout
Considerations
For the best results, it is recommended to physically place the battery pack as close as possible to
the AAT3687 BAT pin. To minimize voltage drops
on the PCB, keep the high current carrying traces
adequately wide. For maximum power dissipation
of the AAT3687 3x3mm TDFN package, the metal
substrate should be solder bonded to the board. It
is also recommended to maximize the substrate
contact to the PCB ground plane layer to further
increase local heat dissipation. Refer to the
AAT3687 evaluation board for a good layout example (see Figures 4 and 5).
AAT3687 Evaluation Board Layout
Figure 4: AAT3687 Evaluation Board
Component Side Layout.
18
Figure 5: AAT3687 Evaluation Board
Solder Side Layout.
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
AAT3687 Evaluation Board Schematic Diagram
ADP
GND
1
2
C1
10μF
J1
ON/OFF
RED
GRN
RED
LED D3 LED D2 LED D1
1 2 3
R3
4.99kΩ
R4
4.99kΩ
R5
4.99kΩ
R7
1kΩ
R1
Open
(TDFN33-12)
U1
2
BAT
TS
GND
1
1
3
2
4
ADP
BAT
EN
ADPP#
STAT2
STAT1
DATA
5
8
9
7
DATA
AAT3687
ADPSET
C2
10μF
6
R2
10kΩ
12
TS
GND
3
CT
10
R6
8.06kΩ
SW1
C3
0.1μF
CT
3687.2006.06.1.5
19
AAT3687
Lithium-Ion/Polymer Battery Charger
AAT3687 Evaluation Board Bill of Materials (BOM)
Quantity Description
1
1
Footprint
Manufacturer
Part Number
DATA
ADP, GND
PAD
TBLOK2
Mill-Max
Phoenix Contact
6821-0-0001-00-00-08-0
277-1274-ND
BAT,
GND, TS
C1, C2
TBLOK3
Phoenix Contact
277-1273-ND
0805
Murata
490-1717-1-ND
C3
0603
Murata
478-1244-2-ND
D1, D3
1206LED
2
Test Pin
Connecting Terminal Block,
2.54mm, 2 Position
Connecting Terminal Block,
2.54mm, 3 Position
Capacitor, Ceramic, 10μF
6.3V 10% X5R 0805
Capacitor, Ceramic, 1μF
10% 25V X5R 0603
Typical Red LED, Ultra-Bright
1
Typical Green LED
1
1
Header, 3-Pin
J1
Resistor, 10kΩ, 1/16W
R2
5% 0603 SMD
Resistor, 4.99kΩ, 1/16W
R3, R4, R5
1% 0603 SMD
Resistor, 8.06kΩ, 1/16W
R6
1% 0603 SMD
Resistor, 1kΩ, 1/16W
R7
5% 0603 SMD
Switch Tact 6mm SPST
SW1
H = 5.0mm
AAT3687 Lithium-Ion/Polymer
U1
Battery Charge Controller
1
2
1
3
1
1
1
1
20
Desig.
D2
Chicago Miniature
Lamp
1206LED
Chicago Miniature
Lamp
HEADER2MM-3 Sullins
0603
Panasonic/ECG
CMD15-21SRC/TR8
CMD15-21VGC/TR8
6821-0-0001-00-00-08-0
P10KCFCT-ND
0603
Panasonic/ECG
P4.99KHTR-ND
0603
Panasonic/ECG
P8.06KHCT-ND
0603
Panasonic/ECG
P1.0KCGCT-ND
ITT Industries/
C&K Div
AnalogicTech
CKN9012-ND
Switch
TDFN33-12
AAT3687IWP-4.2
3687.2006.06.1.5
AAT3687
Lithium-Ion/Polymer Battery Charger
Ordering Information
Trickle Charge
Package
Marking1
Part Number (Tape and Reel)2
Yes
TDFN33-12
PIXYY
AAT3687IWP-4.2-T1
No
TDFN33-12
RTXYY
AAT3687IWP-4.2-2-T1
All AnalogicTech products are offered in Pb-free packaging. The term “Pb-free” means
semiconductor products that are in compliance with current RoHS standards, including
the requirement that lead not exceed 0.1% by weight in homogeneous materials. For more
information, please visit our website at http://www.analogictech.com/pbfree.
Package Information
2.40 ± 0.05
Detail "B"
3.00 ± 0.05
Index Area
(D/2 x E/2)
0.3 ± 0.10 0.16 0.375 ± 0.125
0.075 ± 0.075
3.00 ± 0.05
1.70 ± 0.05
Top View
Bottom View
Pin 1 Indicator
(optional)
0.23 ± 0.05
Detail "A"
0.45 ± 0.05
0.1 REF
0.05 ± 0.05
0.229 ± 0.051
+ 0.05
0.8 -0.20
7.5° ± 7.5°
Option A:
C0.30 (4x) max
Chamfered corner
Side View
Option B:
R0.30 (4x) max
Round corner
Detail "B"
Detail "A"
All dimensions in millimeters.
1. XYY = assembly and date code.
2. Sample stock is generally held on part numbers listed in BOLD.
3687.2006.06.1.5
21
AAT3687
Lithium-Ion/Polymer Battery Charger
© Advanced Analogic Technologies, Inc.
AnalogicTech cannot assume responsibility for use of any circuitry other than circuitry entirely embodied in an AnalogicTech product. No circuit patent licenses, copyrights, mask work rights,
or other intellectual property rights are implied. AnalogicTech reserves the right to make changes to their products or specifications or to discontinue any product or service without notice.
Customers are advised to obtain the latest version of relevant information to verify, before placing orders, that information being relied on is current and complete. All products are sold subject to the terms and conditions of sale supplied at the time of order acknowledgement, including those pertaining to warranty, patent infringement, and limitation of liability. AnalogicTech
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AnalogicTech and the AnalogicTech logo are trademarks of Advanced Analogic Technologies Incorporated. All other brand and product names appearing in this document are registered trademarks or trademarks of their respective holders.
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830 E. Arques Avenue, Sunnyvale, CA 94085
Phone (408) 737-4600
Fax (408) 737-4611
22
3687.2006.06.1.5